Gripping device for testing machines and the like



June 1o, 1924. 1,496,803

A. AMSLER GRIPPING DEVICE .FOR TESTING MACHINES AND THE LIKE Filed May 51. 192.1 2 sheets-sheet 1v r "0. mz..

@2f-FE June 10 1.924.

A. AMsLER GRIPPING DEVICE FOR TESTING MACHINES ANDTHE'LIKE Filed May 51. 1921 2 sheets-sneer 2 Imi ALFRED AMSLER,

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enrrrrivc nnvron For. TESTING MACHINES 'AND 'run Linn `Appumrtm mea may s1, 1921. serial No. 414,011.5

To all whom it may concer/n.:

Be it known that I, ALFRED AMsLER, a citizen-of the Republic of Switzerland, re'- siding at Schaffhausen, Switzerland, have s invented certain new and useful Improvements in Gripping Devices for T sting Machines and the like; and I do here y declare the following to be a clear, full, and exact' description of the invention, such as Will4 enable others skilled'n the art to which it appertains to, make and use the same, reference being had to the accompanying drawings, and to lettersiorfgures of reference marked thereon, which forma part of this specification The invention comprises improvements in gripping devices fortesting machines, the object of which is in theii'rst place to grip wire ropes or hemp ropes of circular crosssection in testing machines in such a manner, that the rope is held tight up to vthe breaking point without 'slipping or getting -damaged at the ends, whereby no special preparations on the rope ends are necessary ..25 for the test. As the rope will not be damaged at the place of gripping the device will be suitable also for testing ropes which are not to be stretched to the breakmg point, but

which have to undergo a trial load along the whole lengthbefore they are taken into use,

which is very'desirable especially for hauling ropes and shi Y. hawsers;

According to t e resent inventionu each end of -the test piece 1s held in the-gripping device in a self-adjusting chuck, the latter is tightened by means of the stress acting upon the test piece each end being embedded 1n a layer or linin of softer material than the test piece itse f, the self-adjusting chuck 40 holding this linln ,into which the surface of the test piece 1s thereby impressed and consequently any slipping of the test piece between the lining revented.

, It is presumed, t at .the friction between the lining and the test piece is at the start already so great that the latter will not slide within the former but will be gripped more tightly by the closing of the chuck.

This automatic gripping certainly takes place ifthe test piece 1s hard or has a rough or uneven surface and in the absence of g lubricants. But-if Athe test pieceis soft and its form is Alost under moderate pressure, as s for instance in the case of a hemp ro e, or if i5w the test piece is saturated with`a lu ricant,

formarse-whaling IOP@ 0f Steel Wires which hs been in use, thenithe starting friction'between the test piece and the linings will not lbe sufficient tov prevent slipping between the two. In such cases, the'automatic gript0 ping chucks are so tightened by an lauxiliary tightening device that the surface of vthe test piece wlll be impressed into the linings of softer material, before the test piece itself is put under testing stress., The auxiliary tightening device is thereby independent from the test piece Furthermore a safety device is provided preventing the p loosening of th'e gripping chucks after the auxiliary tighteningidevice has been drawn out of avction.-` The impressions resulting from' the auxiliary -device prevent the "test piece from slipping in' the linings from the very beginning of the test. .l When the test goes on,` the surface of Ithey test'piece is 75 pressed still deeper into the 'linings by the 'automatic closing of the chucks whereby the resistance against slipping increases with the load." The aforesaid also holds' good fork test pieces with asmooth surface. By suiiiciently tightening the linings any unevennesses of the surface of the material'will be gripped in the softer linings and held4 thereby. l L

l If thev test piece is elastic, for instance B5 a hemp rope,-` or if the lining itself is elastic there will be a tendency forthese elasticities to cause the self-adjusting chucks to open and the pressure between the linings and the test piece to ybe reduced. Therefore, in such 90 cases it is necessary to provide means which f will prevent the opening of the self gri ping chucks .after the auxiliary tightening evice has been drawn out of action and before the testing load secures the further gripping of the chucks.

The accompanying drawings illustrate examples of construction of this invention.

Fig 1 is a plan of one construction of the grilpping device, partly in section; lo

' ig. 2 is a vertical section on Ithe line H-II of Fig. 1.

Fig. 3 is a plan similar to Fig. 1 provided with a special "auxiliary tightenin device.

Fig. 4 1s a vertical section along line IV-r Wofliig.

Fi 5 1s a horizontal section along line V- of Fig. 3. i

Fig 6 is a plan similar to Fig. 1 provided with 'a special auxiliary tightening device and a safety' device against the loosening of the jaws.

i two hoo r stripsvE Fig. is-aahorizontal section along line virvn of rig. e and Fig. 8 is a vertical section lalong line Vllll-Vlllt'of Fig. 6. j

Figs. 1 and 2 show the gripping of a rope of circular cross-'section which is to be tested intension. The self adjusting chuck consists of wedges A provided with teeth A at the facing sldes, the wedges A sliding in the wedge shaped mouth B thereby closing the teeth'A gripping and engaging the parts C which, for example, maybe made 0f wood. rlhese wooden strips form soft layers or linings for the test rope D which will be pressed in during the outward wedges A in the mouth B.

The Figs. 3, 4C and 5 show a gripping device provided with a special auxiliary tightening device, wherein the test piece (here a flat bar) is impressed into its linings before the test piece itself is put under stress. rllhe auxiliar tightening device consists of the or coupling the wedges A of the two chucks, in such a manner that they f move forwards within .the wedge shaped mouths-B `and grip the test piece `while the mouths are moving one away from the other. `During this operation the hook strips Flnot the test piece-overcome the resistance of the Wedges. f

The gripping device illustrated in Figs. 6-8 is slmilar t'o the device shown in Figs. 3 5, butta safety device to prevent the loosening of the chucks is provided which consists of the wedges F which are inserted behind and across the wedges A within the mouths B, thus preventing the backward mpvement of A. 1,

After the linings have been ressed on to the test pieces as aforesaid, t e two hook strips E are removed andthe test proper may be started.

A gripping device according to the invention is not only suitable for rropes, but also for chains, profiled rods, flat or vrolind bars and the like which are 'to`he testedin tension f or torsion, or in tension and torsion without damaging the same at the places wherethey d S N sliding of the incase-s are gripped. This gripping device may also i be adapted for compression tests b' revers-y ing the inclination of the sides of t e chuck, whereby the ends of the test pieces cannot "be supported. lt claim: 1. lln a gripping 7device for testing machines. the combination of metallic chnclrs arrangedv to adjust vthemselves 'automatically under the testing tensional load; of Wooden linings held. by said chucks and between which the piece to be tested becomes embedded without injuring the test piece.

2. ln a gripping device\for testing machines and the like, the combination of chucks adapted to adjust themselves under testing load andconsisting of wedge shaped mouths and Wedges slidin in said mouths, linings rof softer material t an the test piece' itself,.itted` to said wedges and impressed with the surface of the test piece ends so as to prevent the latter from slipping in the l linings, a special auxiliary tightening device consisting ofhook strips operatively connected to said wedges for impressing the surface of the test piece ends into the linings before the test piece itself is ut under testing stress, and means' inserte the thicker ends of said wedges and the wedge shaped mouth for preventing the liners from becoming loosel whensaid hook strips have Nbeen talfen o' and before the testing load Vprovides for a further grip of the self-adjusting chucks between 3. ln a gripplngy device for testing mai chines, the combination of a pair of chucks Y self-adjusting under tension load and comprising wedge-shaped mouths, gripping wedgesslidable in said mouths, linings for said wedges,-'and transverse wedges between the thicker ends of the gripping wedges .and

said moli-tbs to follow up the movement of said gripping wedges due to testing conditions. c

lln testimony that claim the foregoing as my invention, llhave signed myyname.

- ALFRED AMSLBB, 

